Asbestos paper containing carbon and method of making it



United States Patent M 3,269,889 ASBESTOS PAPER CONTAINING CARBON AND METHOD OF MAKING IT Marsden C. Hutchins, Bound Brook, N.J., assiguor to Johns-Manville Corporation, New York, N.Y., a corporation of New York No Drawing. Filed Jan. 2, 1963, Ser. No. 248,864

Claims. (Cl. 162-155) This invention relates to a novel paper product and more particularly to an asbestos sheet or web such as paper and millboard which contains throughout major proportions of particulate carbonate, and means of producing the same.

The primary object of this invention is to produce a high bulk density asbestos paper of good strength properties which embodies up to approximately 75% by weight thereof of particulate carbon.

It is also an object of this invention to provide an asbestos paper of a composition or comprising constituents which entrain and retain high concentrations or proportions of carbon particles while retaining sufiicien-t porosity and ample web strength to permit drainage and normal sheet formation with a conventional paper manufacturing machine and process.

It is a further object of this invention to provide a paper composition which can retain up to about 75% by weight thereof of carbon filler while at the same time maintain sufiicient strength and porosity to be handleable and workable in conventional continuous saturation processes employing resin bath submersion techniques followed by tower drying and curing, and to thereby take up and hold appreciable amounts of higher molecular weight resin saturants.

It is a still further object of this invention to provide means of producing a carbon containing paper which effects nearly a 100% retention of very high proportions of car-hon filler with normal water-laid sheet forming or manufacturing techniques and apparatus.

These and other objects and advantages -of this invention become more apparent and fully understood from the hereinafter detailed description.

The means and product of this invention in general comprises a flexible sheet of asbestos such as a paper or millboard product which is composed of a combination of specific class of asbestos fiber and synthetic resin size along with the particulate carbon filler.

For the effective practice of this invention the asbestos component is derived from chrysotile, crocidolite and amosite types of fiber which are commonly characterized as harsh and typically consist of asbestos fibers having a surface area of about 10,000 to 12,000 cm. /gram. Fibers of this category are refined or beaten until substantially free of any unopened bundles, clumps or pencils of about inch or more in diameter which in turn extends their surface area, or in other words to the point of possessing a Schopper-Riegler freeness test value of at least 180 and preferably of approximately 350 to 560 ml. Further, for optimum effects the asbestos fiber should be sized at least 70% by weight thereof retained on 200 mesh standard screen sieve with at least about 50% by weight of said fiber retained on 200 mesh standard screen sieve passing 28 mesh standard screen sieve and retained on 100 mesh standard screen sieve, based upon a standard Bauer-McNett test.

The size comprises acrylic resins, urea formaldehyde resins, melamine formaldehyde resins, and synthetic 3,269,889 Patented August 30, 1966 resins of like characteristics as for example polyvinyl acetate, polyvinyl chloride, but preferably acrylic resins such as Rohm & Haas Co.s Rhoplex WG-9 or H-16. These resins may be obtained and employed in liquid, solid particulate or emulsion form and most conveniently applied in an aqueous emulsion which is readily dispersible with the fiber in a paper beater or the like apt mixing means.

Paper makers alum-aluminate sulfate-as is usual, aids in coagulating the solids of the slurry or suspension of stock facilitating the web or sheet formation and as such comprises a typically desirable component. Moreover, with some resin compositions such as urea formaldehyde, alum facilitates their retention and cure.

The carbon filler may consist of any particulate or powdered carbon including carbon fiber, flakes, or other forms of powdered carbon materials, and particularly the graphite form of carbon. The flaked or powdered materials are usually sized less than about 200 mesh and more expediently less than 300 mesh standard screen sieve. When the carbon particles are of fibrous form, the quality or nature of the asbestos fiber is of diminishing significance.

Additionally, small quantities as for example about 1-3% by weight of agents such as urea formaldehyde or melamine formaldehyde resins, carboxymethyl cellulose, starch, vinyl alcohol and the like may be included in the stock to enhance the hot wet strength of the product. Moreover, fibrous materials other than asbestos and carbon can be employed to advantage to impart greater strength and/or with inferior categories of asbestos. These include nyl-on (polyamide resin) and other synthetic fibers, natural fibers such as cotton linter or wood fiber, :and inorganic fibers.

It has been found that an aqueous slurry or suspension of a paper stock comprising a combination of materials or components of the foregoing characteristics in the effective ratios of: approximately 15 to 60%, and preferably about 20 to 50% by weight of the particular asbestos fiber; approximately 2 to 10%, and preferably about 3 to 6% by weight of resin size; approximately 0 to 3%, and normally about 1% by weight of alum, and approximately 35 to and preferably about 60 to 75 by weight of particulate carbon filler, can be formed or integrated into a porous and strong web or sheet pursuant to typical paper manufacturing processes or techniques employing conventional apparatus such as a Fourdrinier or cylinder paper machine with a substantially carbon filler take-up and retention. The combined or concerted effects of these specific components or materials of the like given essential properties and ratios entrain the carbon filler in significantly high or major proportions and integrate the ingredients of the slurry into -a coherent, strong and porous web or sheet which is Well adapted to normal handling in typical manufacturing processes and resin sizing procedures providing a paper product of unique over-all composition and properties.

The following comprises specific illustrations or examples of preferred and typical highly carbon filled asbestos paper compositions and the means or method of this invention, demonstrating the pronounced properties or results thereof. It should be understood that the specific materials and/or their proportions given, and the paper forming techniques or processes referred to, are merely exemplary and not to be construed as limiting the invention to any particular data recited hereafter.

3 EXAMPLE I A high gnaphite content asbestos paper was produced from a stock of:

to the initial amount of asbestos fiber in the stock or furnish21% by weightdemonstrates the high retention and content of the graphite filler achieved through the means of the specified components of the slurry and in turn paper product. Constituents Parts Dry Parts Wet Batch,

by Weight by Weight Pounds EXAMPLE II b d M 21 21 168 A number of sets of paper sheets were formed with g: %,f g 5 35: varying proportions, sources and types of carbon mate- No. 4874 Char1es ,2 75 600 rials with the balance comprising harsh chrysotile i gfig fg ggfgg fi fi asbestos, grade 4A, beaten to a SchoppePRiegler tree- PC0.) 3. 1 ness of about 400 ml., in combination with 3% by weight 1,5431, 13,300 of acrylic resin emulsion, and 1% by weight of alum. T H 100 1 657 0 14 000 The amount, type and source of the carbon fillers em- 0 a ployed in thme papers and their resulting physical prop- 1 Dry erties were as follows:

Table II Samples A B C D E F G H I J K L M Furnish, percent:

Asbestos fiber 48 68 48. 5 68 46 21 40 21 46 21 46 21 46 Graphite textile fiber (WA. 0007,

National Carbon Co.) 48 28 in. Chopped graphite thread WFA, National Carbon 00.).. 50 75 Powdered graphite flake (Type 40, No. 4874 Charles Pettenos, Inc.) 48. 5 29 50 75 Carbon filler (Type 163, Keystone) 50 75 Chopped carbon thread, to

in. (H. I. Thompson Co.) 50 75 Carbon pigment paste (Aquablaek B, Columbia Carbon o0.) 50 Acrylic resin 3 3 3 3 3 3 3 3 3 3 3 3 3 Alum 1 1 1 1 1 1 1 1 i 1 1 Physical Properties:

Basis weight, lb. /100 it. 3. 2 3. 3 3. 1 3. 3 3. 2 3. 0 3. 5 3. 0 3.1 2. 7 3. 2 3. 5 3.4 Caliper, mils 15 12 13 13 9 22.5 27 15 10 32 i5 Bulk, percent. 0.47 0.45 0.39 0.41 0.41 0. 0.65 0.89 0.49 0. 37 0.63 0.92 0.44 Mullen, .s.i.-. 4 4 4 a 4 3 2 1 4 3 4 2 7 Tensile, lb./in 5.2 5.5 5.4 4.5 3.9 1.9 3.9 2.6 4.1 2.8 4.2 2.8 7.8 Stretch, percent 0. 8 0. 8 0. 6 0. 4 2. 0 2. 5 0. 6 0. 5 1. 8 2. 9 1. 1 0. 6 0. 7 Wet (water) tensile, 1b./in 2. 7 2. 7 2.1 1. 4 1. 5 1. 1 1. 1 1. 3 1. 7 0. 8 1. 2 1. 7 2. 7 Wet (methylethyl ketone) tensile,lb./in 1.9 2.1 1.7 1.7 1.5 0.7 1.2 0.4 1.3 1.5 0.8 0.7 4.5 Tear, grams..- 32 30 31 31 23 34 45 38 24 34 38 40 20 Stiffness, grams-.. 1. 1 1. O 0. 6 0. 7 0. 4 0. 2 1. 5 2.1 0. 4 0. 2 1. 1 1.8 3. 4 Densometer, see/1000 20 28 19 27 28 22 5 22 12 10 i 600 Kerosene value, percenL- 153 150 100 114 101 90 198 345 100 84 190 357 82 Ash, percent 43.2 60.1 45.5 01.1 21.9 41.2 20.0 48.6 39,7 40.6 Asbestos, percent 49.9 69.4 52.8 70.7 25. 47.6 23.1 56.2 45,8 46.9

The asbestos fiber, having a surface area of 10,000 to In each case the carbon and graphite filled papers were 12,000 cm. /gram was added to a beater and beaten until similar in streng those embodying carbon in a substantially free of unopened fiber bundles and thereby fibrous form were generally of increased bulk, porosity rendered to a Schopper-Riegler freeness of 330 ml., the and kerosene saturation. All sheets drained fast and carbon graphite added and mixed for 10 minutes, folthe retention of the powders as Well as the fibers was lowed by the addition of the acrylic resin and a 5 minute nearly 100%. mix, and finally the alum added. Upon completing the The high carbon and graphite content asbestos papers admixing f the components th slurry a dil t d and of this invention are particularly useful in the manu- .a water-laid felt or sheet thereof formed on a Fourdrinier factllre Of high resin content laminates or structures for ma hin F thi papa two samples were i -1 transient thermal insulation applications. Their adaptaexa i d, i i th f ll i h i l properties; bility and effective resistance and properties to the rigor- Table l ous c0nd.it1ons encountered in such high temperature applications are demonstrated by the following compara- Physical Properties Sample A Sample B tlve tests- EXAMPLE HI Basis weight, lb./100 it 2 8. 6 10. 3 Cal1per,mils 25 29 High graphite content asbestos papers composed of Bulkmercent 0.29 0.28 d 3 4 ftfi 5 8 gra e W or A chrysotile fiber, 3% by weight acrylic ensi e, .in. M 4.2 6.8 re in Tensile, 1mm 3.3 53 11s I; and in some nstances 1% by Weight alum, with gg g g t; 6 1 L7 13 t e-fallance the indicated proportions of gnaphite, were re c ,perceii 1.9 3.0 ar i Wet (water)tensilelbfimMDnm 1.6 20 g e 111 y hand saturatedproviding approximately 40% wggsmethylethyl ketone) tensile Ill/m y weight of phenolic resin content throughout and lami- 1.3 1.7 1 Teangmms MD 24 30 gigte d to a thickness of A inch, then cured 1 hour at getygrams CDM.1 25 32 0 under 400 P- Samples of a Control paper to i ness, grains 1.8 3.2 i Stiffness, grams CD L 6 27 PYOVlde a standard f r c mparative evaluation, composed gensometerisewmo ie 46 73 of 97% by weight of grade 3W chrysotile asbestos and erosene va ue, percen 78 74 i i Asbestosbyashtestypement 205 by Wmght f acrylic sin wa likewise saturated with 40% by weight of phenolic resin and sub ected to 0115113 depotes machinedireetiorr or parallel to the web formation, and a hke cure' Both the graphite Containing and the as estos The em;J es tc(r)oss maihinte diii etcltlion or perpendicular to web formation control papers were then subjected to an oxy-acetylene as es s con en 0 e paper as determined by ash torch test wherein the oxygen and lacetylene pressure tests, i.e., 20.7 and 20.5% by weight thereof, in relation 75 gauges were regulated to 40 p.s.i. and 10 p.s.i., respec tively and the tip of a torch maintained at a distance of 1% inches from the center of 6 x 6 x 4 inch test samples of each paper. The time was recorded for the cold face temperature of the samples to reach 400 F. by locating a thermocouple on the cold side of the sample, and the time for the flame to burn completely through the sample Table I V.Ablati0n test data 60 second Exposure Time (Avg. of 2 samples or 90 second Exposure Time (one sample) single samp.)

Sam- Paper Reinforce- Resin Sp.

ple ment Description (percent) Gr. Erosion Rate Mass Ablat. Cold Erosion Rate MassAblat. Eff. Cold Rate E11. Heat Face Rate Heat Face (lbjitfl- Cap. Temp. (lb./it.*- Cap. Temp. Mils/ Grn./ sec.) (B.t.u./lb.) Rise Mils/ Gm./ sec) (B.t.uJlb.) Rise sec. sec. F.) sec sec. F.)

A Carbon Cloth 50 1.33 2.83 0.303 0.0196 20, 400 208 2.73 0.273 0.0189 21,200 340 B "do 1.28 3.03 0.245 0.0202 19,700 673 2.92 0.206 0.0194 20, 600 1,888 O... Graphite Cloth 48 1.29 3.06 0.235 0.0206 19,500 790 3.10 0.209 0.0208 19,200 1,603 D- 75% Graphite Powder-Asbestos. 1.58 2.70 0.279 0.0222 18,000 169 3.03 0.281 0.0249 16, 100 306 E Graphite 46 1.49 3.33 0.287 0.0258 15, 500 67 3.42 0.283 0.0264 15, 200 115 Fiber-Asbestos. F--- 50% Chopped Tex- 50 1.40 3.68 0.291 0.0268 14, 900 63 3.62 0.283 0.0264 15, 200 112 tile Graphite Fibcr-Asbestos. G 50% Graphite 44 1.63 3.32 0.318 0.0281 14, 300 92 3.23 0.280 0.0274 14,600 108 Powder-Asbestos. H---" 75% Graphite 44 0.99 5.63 0.268 0.0290 13, 800 870 5.55 0.233 0.0286 14,000 1,953

Fiber-Asbestos. I 75% Carbon Pow- 42 1.35 4.82 0.257 0.0338 11,800 99 4.11 0.237 0.0288 13,900 140 tier-Asbestos. J 75% I(garbon Fiber- 44 0.86 6.33 0.259 0.0339 11,800 968 5.86 0.228 0.0314 12, 700 1, 992

As estos. K 50% garbon Fiber- 44 1.18 5.73 0.349 0.0351 11, 400 88 5.74 0.314 0.0352 11, 400 845 As estos. L 50% Carbon POW- 42 1.44 5.14 0.291 0.0384 10,500 95 5.60 0.286 0.0419 9,600

der-Asbestos.

was also recorded. The compositions of the control and the various asbestos and graphite containing asbestos fiber- The high carbon filler content retention capacity, good physical properties and in particular porosity and high resin laminate samples and their respective erosion rates 35 resin saturant capacity of these papers and in turn their were as follows:

effectiveness in laminations for high temperature ablative Table III Time to Time to Erosion Insllation Resin Laminate Paper Thickness, 400 F. Burn Rate, Index, Reinforcement Compositions in. (sec.) Tl(irou)gh mil/sec. mil/sec.

sec.

Control:

Asbestos 97% 0.240 72 76 3 .195 3 .3 Acrylic resin 3% Asbestos 48% 0 .297 68 120 2 .48 4 .37 Graphite fiber 48% Acrylic resin 3% Alum 1% Asbestos 68% 0 .281 92 3 .05 4 .68 Graphite fiber. 28% Acrylic resin 3% Alum 1% Asbestos 48.5% 0.255 60 104 2 .45 4 .25 Graphite flake.-. 48.5% Acrylic resin 3.0%

Asbestos 68% 0 .239 64 92 2 .60 3. 73 Graphite flake. 29% Acrylic resin 3% 1 Erosion rate calculated by dividing sample thickness in mils bytime for sample to burn through in seconds. 2 Insulation index calculated by dividing the sample thickness in mils by time for the cold face to reach 400 F EXAMPLE IV 40 kw. Giannini Model L-40 Plasmatron powered by four selenium rectifiers. The following conditions were used on the test samples: heat flux of 400 B.t.u./ft. -sec.,

insulations, among other advantageous attributes, are all demonstrated by the foregoing examples.

It is to be understood that the foregoing details are given for the purpose of illustration .and not restriction and that variations within the spirit of this invention are to be included within the scope of the appended claims.

I claim:

1. A high bulk asbestos paper product consisting essentially of at least about 15% by weight of harsh asbestos fiber having a Schopper-Riegler freeness value of about 180 to 5 60 ml., approximately 2 to 10% by weight of resin size, and approximately 35 to by Weight of particulate carbon.

2. The paper product of claim 1 wherein the resin size gas enthalphy of 2695 B.t.u./ lb. (average), flame temper- 7 is an acrylic resin.

3. The paper product of claim 2 wherein the particulate graphite comprises powdered flake graphite.

4. A high bulk asbestos paper consisting essentially of approximately 15 to 60% by weight of harsh asbestos fiber having a Schopper-Riegler tfreeness value of about 180 to 560% ml., approximately 2 to 10% by weight of resin size, and approximately 35 to 80% by weight of particulate carbon.

5. The paper product of claim 4 wherein the resin size is an acrylic resin.

6. The paper product of claim 5 wherein the particulate graphite comprises powdered fiake graphite.

7. A high bulk asbestos paper consisting essentially of approximately 20 to 50% by weight of harsh asbestos fiber having a Schopper-Riegler freeness value of about 180 to 560 ml., approximately 3 to 6% by weight of resin size, and approximately 50 to 80% by weight of particulate carbon.

8. The paper product of claim 7 wherein the resin size is an acrylic resin and the particulate graphite comprises powdered flake graphite.

9. The paper product of claim 8 wherein the asbestos fiber is sized at least 70% by weight retained on 200 mesh standard screen sieve, and at least about 50% by weight of said fibers retained on 200 mesh standard screen sieve pass 28 mesh standard screen sieve and are retained on 100 mesh standard screen sieve.

10. A high bulk asbestos paper consisting essentially of about 22% by weight of harsh asbestos fiber having a Schopper-Riegler freeness value of about 180 to 560 ml., about 3% by weight of (acrylic resin size, and about 75% by weight of powdered flake graphite.

11. The method of producing high bulk density asbestos paper containing major amounts of particulate graphite, said method comprising forming a dilute aqueous suspension consisting essentially of at least approximately 15% by weight of refined harsh asbestos fiber having a Schopper-Riegler freeness value of about 180 to 560 ml., approximately 2 to 10% by weight of resin size, and approximately 35 to 80% by weight of particulate gnaphite, then forming therefrom a water-laid sheet of paper.

12. The method of claim 11 wherein the resin size is an acrylic resin.

13. The method of claim 12 wherein the graphite comprises powdered graphite flakes.

14. The method of producing high bulk density asbestos fiber containing major amounts of particulate graphite, said method comprising forming a dilute aqueous suspension consisting essentially of approximately l5 to by weight of refined harsh asbestos fiber having a Schopper-Riegler freeness value of about 350 to 560 ml., approximately 2 to 10% by weight of resin size, and approximately 35 to by weight of particulate graphite, then forming therefrom a water-laid sheet of paper.

15. The method of claim 14 wherein the resin size is an acrylic resin.

16. The method of claim 15 wherein the graphite comprises powdered flake graphite.

17. The method of producing high bulk density asbestos paper containing major amounts of particulate graphite, said method comprising forming a dilute aqueous suspension consisting essentially of approximately 20 to 50% by weight of refined harsh asbestos fiber having a Schopper-Riegler freeness value of about 350 to 560 ml., approximately 3 to 6% by weight of resin size, and approximately 50 to 80% by weight of particulate graphite, then forming therefrom a water-laid sheet of paper.

18. The method of claim 17 wherein the resin size is an acrylic resin.

19. The method of claim 18 wherein the graphite comprises powdered flake graphite.

20. The method of claim 19 wherein the asbestos fiber is sized at least 70% by weight retained on 200 mesh standard screen sieve, and at least about 50% by weight of said fibers retained on 200 mesh standard screen sieve pass 28 mesh standard screen sieve and are retained on mesh standard screen sieve.

References Cited by the Examiner UNITED STATES PATENTS 2,485,458 10/1949 Quinn l62l55 3,022,213 2/1962 Pattilloch 162-18l 3,034,981 5/1962 Poelman l62155 DONALL H. SYLVESTER, Primary Examiner.

MORRIS O. WOLK, Examiner. H. R. CAINE, Assistant Examiner. 

1. A HIGH BULK ASBESTOS PAPER PRODUCT CONSISTING ESSENTIALLY OF AT LEAST ABOUT 15% BY WEIGHT OF HARSH ASBESTOS FIBER HAVING AT SCHOPPER-RIEGLER FREENESS VALUE OF ABOUT 180 TO 560 ML., APPROXIMATELY 2 TO 10% BY WEIGHT OF RESIN SIZE, AND APPROXIMATELY 35 TO 80% BY WEIGHT OF PARTICULATE CARBON.
 11. THE METHOD OF PRODUCING HIGH BULK DENSITY ASBESTOS PAPER CONTAINING MAJOR AMOUNTS OF PARTICULAR GRAPHITE, SAID METHOD COMPRISING FORMING A DILUTE AQUEOUS SUSPENSION CONSISTING ESSENTIALLY OF AT LEAST APPROXIMATELY 15% BY WEIGHT OF REFINED HARSH ASBESTOS FIBER HAVING A SCHOPPER-RIEGLER FREENESS VALUE OF ABOUT 180 TO 560 ML., APPROXIMATELY 2 TO 10% BY WEIGHT OF RESIN SIZE AND APPROXIMATELY 35 TO 80% BY WEIGHT OF PARTICULATE GRAPHITE, THEN FORMING THEREFROM A WATER-LAID SHEET OF PAPER. 